1.1 defensive barriers

types of transmission

horizontal & vertical

horizontal transmission

transmission between animals which are not connected foetally

vertical transmission

direct contact (pathogen crosses placental barrier, infecting foetus)

why is external epithelium more susceptible to disease?

trauma & infection

why is mucous membranes more susceptible to disease?

thin walls required for physiological function

how does skin protect from infection/disease?

• keratinocytes replicate to general stratified squamous keratinised epithelium
• has receptors binding to microbes causing signalling cascade (inflammation triggered)

cells produced during inflammation

cytokines (immunological hormones)
chemokines (cell migration factors)

melanocytes

protects skin from uv damage

langerhaan cells

• regulates immune system
• tissue resistance macrophages present in all layers of epidermis
• early warning system for immune system, move quickly to lymph nodes

sebum & sebaceous glands

• contains fatty acids (water repellant)
• anti-microbial properties

mucociliary escalator

• continual movement of cilia in resp. tract
• stops colonies forming by moving them continually

the 4 epithelial barriers

• physical - skin
• physiological - mucous membranes
• biochemical - gastric acid
• immunological - macrophages

oral cavity/oesophagus epithelial cell type?

stratified squamous epithelium

biochemical barrier of oral cavity/oesophagus?

lysozyme in saliva

paneth cells

specialised secretory epithelial cells in small intestine

produce granules (cryptidins) containing antimicrobial peptides & immunomodulating proteins which regulate composition of intestinal flora

how does the small intestine protect from infection?

contains cryptidins

cryptidins

synthesised by paneth cells
fights bacterial & fungal pathogens